I. Field of the Invention
The present invention relates generally to valve assemblies and, more particularly, to a bypass valve assembly for a fluid flow meter.
II. Description of the Prior Art
There are a number of different types of fluid flow meters. In general, however, fluid flow meters comprise a housing having an inlet, an outlet and a fluid passage formed through the housing for fluidly connecting the inlet to the outlet. A flow responsive member is mounted within the housing in series with the fluid passage so that the position of the flow responsive member varies in accordance with the fluid flow rate through the flow meter. Indicator means provide an external signal of the position of the flow response member and thus of the fluid flow rate.
Flow meters are conventionally designed to operate over a predetermined range of fluid flow rates. Furthermore, if the maximum fluid flow rate for the flow meter is exceeded, particularly by a large amount, the flow meter is oftentimes damaged thus requiring expensive repair and/or replacement.
For many applications, however, the user of the flow meter is desirous only of determining when the fluid flow rate falls below a predetermined and relatively low flow rate. Such low flow rates are typically indicative of a clogged system or other malfunction of the fluid system. At the same time, however, the flow meter must be capable of operating under relatively high fluid flow rates without damaging the flow meter although the actual flow rate above the predetermined minimum flow rate is unimportant.
For such fluid applications, the use of a flow meter having a relatively high fluid flow range has not proven wholly satisfactory. First, flow meters with high flow ranges are relatively expensive in construction and thus uneconomical for the user who desires to determine only when the flow rate falls below a predetermined minimum amount. Secondly, the accuracy of many flow meters decreases proportionately with the range of fluid flow rates of the flow meter. Thus, a flow meter with a very high flow range is incapable of accurately measuring relatively low fluid flow rates.